JPS6142895A - Thin film el panel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a thin film EL panel among flat display panels that will become increasingly necessary in the future, especially in the field of office automation, in line with the trend of information society. be. Unlike liquid crystal or electrochromic display panels, EL panels are all-solid-state, self-luminous, easy to see even in the dark, and less dependent on viewing angle. In addition, it is thin and lightweight, making it easy to create high-definition screens, and is flicker-free, making it ideal for use as character and graph ink displays for personal computers and word processors.

Conventional Structure and Problems Generally, an EL flat panel has a structure in which a transparent electrode, a first insulating layer, a phosphor layer, a second insulating layer, and a back electrode are laminated in this order on a glass substrate.

The transparent electrode is a mixed crystal oxide of In and Sn, and the insulator layer is Y2O5+ T a 205 , A 120 s
, S l 3N 4°TiO2,5rTtO3,B
aTtO3 and P b T 103 have been conventionally used. Furthermore, ZnS:Mn or ZnS:TbFs is often used as the phosphor layer. In the above configuration, when an orthogonal matrix is formed by striped transparent electrodes and back electrodes and operated in a line-sequential driving method, the brightness of the panel decreases as the number of horizontal 2-in electrodes increases, which is different from the current C- There is a limit to the size of the filter panel. If there are more than 600 horizontal lines, the brightness is insufficient for practical use.

For example, when using a ZnS:Mn phosphor layer, the brightness of an EL panel is determined by the concentration of the
Interface state between ZnS:Mn layer and insulator layer and ZnS:M
It depends on the crystallinity of n. Although there are many unknown points regarding the interface state, the optimum Mn5 degree is approximately 0.8 atoms, and the better the crystallinity, the higher the brightness can be obtained.

As a result of further investigation into factors other than the above-mentioned generally known factors that affect brightness, we found that in the annealing process after forming the ZnS phosphor film, there was It has become clear that elemental diffusion affects brightness. In particular, when the first insulating layer contains an element of Group 4 a of the periodic table, the brightness may be impaired due to diffusion of the element from the underlying layer to the ZnS phosphor layer unless annealing is performed carefully.

OBJECTS OF THE INVENTION The present invention is characterized by providing a thin-film EL panel with higher brightness than conventional ones.In particular, in consideration of manufacturing costs, a low-voltage drive type EL panel uses an insulator layer with a high dielectric constant. However, such insulating layers often contain elements from group 4 a of the periodic table, such as Ti.
In an annealing step after forming the ZnS-based phosphor, these are prevented from diffusing into the ZnS to improve brightness.

Structure of the Invention The present invention is designed to prevent elements from diffusing into the ZnS from the base layer before forming the ZnS-based phosphor layer during an annealing process after forming the layer. A part is composed of Ca S, and this Ca
It was ensured that S was in contact with the phosphor layer. This allows C
aS not only does not diffuse into the ZnS phosphor layer (C
It is possible to improve the brightness of the EL panel by stopping the diffusion of elements from the base before aS is formed. In particular, when the first insulating layer contains elements of Group 4 a of the periodic table, it is possible to effectively stop the elements from diffusing into ZnS and to obtain stable high brightness.

Description of examples Embodiment 1 of the present invention will be described in detail below. 1n, Sn mixed crystal oxide transparent electrode (ITO).

Two substrates formed on glass by direct current activated sputtering using a Sn alloy as a target were prepared. On one side, a Y2O3 thin film of 2,500 layers was formed by EB active evaporation using Y meckle, and on the other hand, a CaS thin film of the same thickness (2,500 layers) was formed using high-frequency sputtering using CaS powder as a target.The substrate temperature for both was 200°C. The gas and its pressure are 02, Ca
S is Ar of 6 x 10-' torr.

In the subsequent manufacturing process, the two substrates mentioned above were created at the same time.
ZnS:Mn phosphor thin film containing
The film was formed to a thickness of 0.03 mm, and then annealed in a vacuum at a temperature of 550° C. for 1 hour.

Next, 2,500 Y2O3 films were formed again using the same manufacturing method, and finally, Al metal was vapor-deposited as a back electrode.The EL panel produced as described above was driven by a 5KHz sine wave, and its voltage and brightness characteristics were measured. It is shown in Figure 1. Curve 1 in the figure is glass/IT O7'Y 203/Zn
S: Mn/Y2O3/IJ panel, 2 is glass/IT
O/Ca S /Z n S :Mn, /'(203/
The characteristics of the A1 panel were shown. Although the thickness of the ZnS:Mn phosphor film is the same, Ca
The brightness of the panel using the S thin film is approximately 1.3 times higher.As a result of examining both ZnS:Mn thin films using QX-ray diffraction, the diffraction intensity of the (111) peak of ZnS:Mn is rather due to the fact that Y2O3 is the underlying material. It was bigger. However, as a result of examining the concentration distribution of the constituent elements along the thickness direction of the ELl panel using secondary ion mass spectrometry (SIMS), it was found that ZnS:Mn
In a panel using Y2O3 as the first insulating layer in the phosphor film, Y and In were diffused from that direction. On the other hand, the first
In panels using CaS as an insulating layer, diffusion of Ca and In is much smaller. Generally, the higher the purity, the stronger the luminescence of a phosphor, so when CaS is used as the first insulating layer, it can be said that contamination of impurities into ZnS is effectively prevented, leading to improved brightness.

Example 2 Sr was deposited on a glass substrate coated with the same ITO as in Example 1.
A TiO3 thin film was targeted to its oxide ceramic at an ao% of 8 x 10''-' torr.
The film was formed to a thickness of 5,000 wafers by high frequency sputtering in an Ar gas containing 2, at a substrate temperature of 400°C. S r T
After applying the 10a thin film, it was divided into two parts, and 500 CaS thin films were further laminated on one half using the same method as in Example 1.

Thereafter, both sheets were treated with ZnS:M at the same time in the same manner as in Example 1.
Stacked with n, Y 20s and Al, E
Finished the L panel. Their voltage and brightness characteristics are shown in curves 3 and 4 in FIG. Curve 3 is glass/ITO/S
r T iOs/Z n S: M n/Y 203
/A l −, 4 is glass /I To/S r Ti
O3/Ca S/Z n S :Mn/Y2O3/A
The characteristics of the ll panel were shown. Since the S r TiO3 thin film has a high dielectric constant of about 140, the emission starting voltage is lower than that in the case of using Y, 203 or CaS as the first insulating layer in Example 1.

From a comparison of curves 3 and 4, the two-layered first insulating layer of SrTiO3+CaS in which CaS is on the ZnS:Mn side has a brightness about 1.8 times higher than that in the case of simply SrTiOs.

The (111) X-ray diffraction peak of ZnS:Mn was compared to that of SrTi.
Comparing the case where it is formed on O3 and the case where it is formed on SrTiO3+CaS, the latter is about 10% stronger. However, as mentioned above, there is a much greater improvement in brightness than that,
This was found by SIMS to be because in the latter case, the diffusion of Ti, Sr, and In elements into ZnS:Mn during the ZnS:Mn annealing process was effectively prevented by the CaS thin film.

In particular, Ti impairs light emission when diffused into ZnS:Mn. Similarly, the Group 4 a elements Zr and Hf have a similar tendency. This was confirmed in a separate experiment.

Example 3 The structure was exactly the same as in Example 2, but a green-emitting ZnS', TbFs phosphor thin film was used instead of ZnS:Mn. 2 wt% TbF3 relative to ZnS
Targeting powder containing 2 x 1O-2to
A ZnS:'rbF's film was prepared by high-frequency sputtering in an Ar atmosphere with a substrate temperature of 200°C. The subsequent annealing temperature is 400° C. for 1 hour. The voltage and brightness characteristics of the EL panel are shown by curves 5 and 6 in FIG.

5 is glass / I T O / S r T :03/
ZnS: TbF3/Y2O3/Al, e
Glass/ITO/SrT: 03/C
ab/ZnS: TbF3/Y, E of 03/A# structure
The characteristics of the L panel are shown. CaS similar to Examples 1 and 2
This effect was observed, and the brightness was improved by about 1.4 times.

Effects of the Invention As described above, according to the present invention, as shown in Example 1.2.3, by using a composite first insulating layer in which CaS or CaS and another insulating layer are stacked, the brightness of an EL panel can be improved. can be increased by about 1.3 to 1.8 times, which is effective in increasing the size of the panel, and can further improve the practicality of the EL panel.

[Brief explanation of the drawing]

The figure is a characteristic diagram for explaining the thin film EL panel of the present invention. Name of agent: Patent attorney Toshio Nakao and one other person Voltage-Y (1-121S)

Claims (2)

[Claims] (1) Laminating a transparent electrode on a glass substrate, a first insulating layer thereon, a ZnS-based phosphor layer thereon, a second insulating layer and a back electrode thereon, and forming the first insulating layer 1. A thin film EL panel characterized in that all or part of the phosphor layer is made of CaS, and the CaS is always in contact with the phosphor layer. (2) The thin film EL panel according to claim 1, wherein the first insulating layer is formed by laminating an oxide containing an element of Group 4 a in the periodic table and CaS.